1. Field of the Invention
The present invention relates to a receiver for wireless communication systems and an I/Q signal phase difference correction (referred to as “phase mismatching calibration”) method therefor, and more particularly to a receiver for wireless communication systems and an I/Q signal phase difference correction method even in an analog signal area so as to easily correct even a large phase difference as well as to reduce time it takes to correct the phase difference.
2. Description of the Related Art
FIG. 1 is a block diagram for schematically showing a receiver for conventional wireless communication systems.
As shown in FIG. 1, the receiver generally includes an amplifier 10, mixers 20, filters 30, analog-to-digital (A/D) converters 40, a phase difference correction unit 50, and so on, for processing a data signal received by an antenna and sent from a transmitter.
The amplifier 10 amplifies a data signal weakened while transmitted in the air, and the mixers 20 remove a carrier signal from the data signal and down-converts the carrier signal into a base band to detect the amplified data signal. The mixers 20 are formed in a pair, and the mixers 20 input a differential signal having the same frequency as the carrier signal and for down-converting the carrier signal to a base band, and generate an I-signal and a Q-signal, respectively. In here, the I-signal is referred to as an in-phase channel signal and the Q-signal is referred to as a quadrature-phase channel signal, and the I/Q signals have a 90° phase difference therebetween.
A pair of such data signals having a 90° phase difference therebetween through the mixers 20 passes through the filters 30, by which noise on the signals is eliminated, and then is converted into digital signals by the A/D converters 40.
Since the I/Q signals from the mixers 20 need to have a phase difference of exactly 90° therebetween, a phase difference correction unit 50 is provided to correct the phase difference between the I/Q signals. As shown in FIG. 2, the phase difference correction unit 50 includes an adder to correct the I-signal by processing a value obtained from multiplication of the I-signal by an arbitrary coefficient a and a value obtained from multiplication of the Q-signal by an arbitrary coefficient b, and another adder to correct the Q-signal by processing a value obtained from multiplication of the I-signal by a coefficient c and a value obtained from multiplication of the Q-signal by a coefficient d. However, such a correction method in the phase difference correction unit 50 is carried out in digitally, which causes problems of difficulties in corrections if a phase difference between the I/Q signals is large and a processing speed is slow due to complicated digital processing.
Accordingly, there is needed a method that can easily correct a phase difference even when the phase difference is large, and can reduce time it takes to correct the phase difference, correcting the I/Q signals in the analog area rather than the digital area.